kv example

This example is using a golang plugin implementation.

You can run the example by:

starting a local temporal cluster

starting the worker:

KV_PLUGIN="python3 ./hashicorp/kv-python/plugin.py" go run ./examples/kv-python/main.go

running the starter:
```
go run ./examples/kv/starter/main.go
```

Check temporal web (http://localhost:8088) for the workflow execution history.